Respective methods and sealing stations are known, for example, from DE 10 2008 023 319 A1 or DE 10 2008 052 423 A1. A hermetically sealed chamber is usually formed between a sealing tool upper part and a sealing tool lower part in order to be able to evacuate and/or to fumigate (i.e. to flush with gas) the packaging units to be sealed. A tray carrier carrying the packaging units can be lifted in order to drive the trays and a top film lying upon these trays against a sealing tool. The top film is sealed onto the trays by the heat of the sealing plate and the pressure created when pressing the sealing tool upper part onto the tray carrier.